And tonight, abc news has an exclusive first look at a new report of interest to shoppers everywhere. Top scientists are revealing that some of the food in our kitchens may be counterfeit. Tonight, abc senior national correspondent jim avila tells us the clues that can tip you off. Reporter: Staples of the grocery aisle. All according to a study to be released tomorrow by usp, a trusted independent lab, frequent targets of fraud. Food products are not always what they purport to be. Reporter:7% of america's food supply now estimated to contain fraudulent ingredients, and this new review of scientific research says these liquids and ground food are most often doctored. Expensive extra virgin oli oil diluted with cheaper vegetable oils. Costly pomegranate juice adulteration widespread, some brands diminished by grape or pear juice. Saffron, black pepper and paprika out with stems and cheaper spices. Tea bags, filled with fern leaves and common lawn grass. Pure lemon juice reduced by sugar and water. One had 10% lemon juice. Another had 15% lemon juice, another had 25%, and the last ONE HAD 35%. Reporter: So what can a consumer do? First, if you can, buy whole products. Tea leaves, coffee beans, whole pepper and grind them yourself. And be careful of super price cuts. That's pretty cheap for extra virgin olive oil. And something that should raise some eyebrows for consumers. Reporter: Both the fda and grocery manufacturers association tell abc news they take the new findings seriously, and monitor grocery aisles for food fraud. Now both have new ammunition to fight it. Jim avila, abc news, washington.

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Consumer Alert: Concerns About Counterfeit Foods

A new report suggests that you might not be getting what you're paying for.

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